Magnetic recording members are traditionally made by spraying or coating onto an appropriately shaped substrate, a fluid mixture of magnetic particles and resinous binder and thereafter curing the resinous binder to adhere the magnetic particles to each other and to the substrate. Examples of such fluid mixtures can be found in U.S. Pat. No. 2,914,480 to Hagopian and U.S. Pat. No. 3,058,844 to Johnston et al. Conventional magnetic recording members contain additional constituents for various purposes. For example, U.S. Pat. No. 3,622,386 to Larsen teaches the addition of an abrasive particle to a magnetic recording element in order to improve the usable life of the element and decrease the hazards of permanent damage to the recording surface and the recording head as a result of an occasional head crash.
Magnetic coating compositions have been made with a wide variety of binder systems both thermoplastic and thermosetting, and many of these magnetic coatings have very desirable properties for particular applications. However, substantially all of the magnetic coatings have disadvantages from the standpoint of their magnetic properties, their physical ability to withstand abrasion, their abrasive effect upon recording heads and their processing characteristics.
Before a tape product can be marketed commercially, it is desirable to perform several tests to determine not only its memory characteristics but also physical characteristics such as abrasive quality. At the present time, there is no existing method which satisfactorily correlates tape abrasion to head wear. Prior to the present invention, a rough correlation could be established by running a tape product through commercial apparatus for an extended period of time, e.g., 24 hours, and then microscopically examining the magnetic head and tape surface for wear. Other abrasive means have been attempted, even using dummy head blocks in which the amount of head material which has been worn from the block was measured, but due to the difficulty in fabricating uniform blocks, such tests have proven to be inaccurate. Existing methods are useful as guides but are time consuming and expensive to run and therefore of little interest as a production or quality control tool on a continuous basis. Furthermore, such a protracted tests results in both magnetic tape wear and magnetic head wear. The magnetic head follows a constant path on the magnetic tape and actually cuts a groove within said tape such that after a protracted period during the test, one is no longer "testing" the commercial tape product but is instead merely running the magnetic head over a smoothed or polished tape surface.